Two-voltage direct-current generator



April 10, 1928. 1,665,691

1.. DREYFUS TWO-VOLTAGE DIRECT CURRENT GENERATOR Filed Feb. 23. 1 927 InI/en for Patented Apr. 10, 1928.

UNITED STATES 1,665,691 PATENT OFFICE.

LUDWIG DREYFUS, OF VASTERAS, SWEDEN, ASSIGNOR TO ALLMKNNA SVENSKA ELEKTRISKA AKTIEBOLAGET, OF VAS'IERAS, SWEDEN, A CORPORATION OF SWEDEN.

TWO-VOLTAGE DIRECT-CURRENT GENERATOR.

Application filed February 23,1927, Serial No. 170,313, and in Sweden December 4., 1924.

An electric generator intended to operate in parallel with a storage battery should, it

a booster. or a reconnection shall not be nec I essary, be ableto deliver two different volt-l ages simultaneously, corresponding to the charging and, discharging voltages of the present invention the generator-is provided with atlleasttwo brush sets'embr'a'ing'zones of different width'jon' the commutator. The ,distribution of the pole arcs, along't'he pe-" .ripliery-of the armature ,is' preferably such that the said periphery is divided in zon cs of the voltage and, tones having a high re having alow reluctance for'the'g'eneration luctan ce for the, commutation. V r A formof the invention is illustrated in I the accompanying drawing. Fi'g. 1 of the is a flux diagram.

The machine illustrated is of a type intended to deliverapractically constant volt this purpose a set of short-circuited brushes, the armature current between which creates the main field. The voltage between the said brushes is produced by an auxiliary field which can be varied according to circumstances. Itmay for instance be generated by two windings counteracting each other, one of which, designated as 1, is fed by substantially constant current from the battery 2 through an iron wire resistance 3 and the other 4 in a manner to be specified. The brushes 5 closing the circuit which serves to generate the main field are four in number (in a two-pole machine) and are short-circuited in pairs in the direction of said main field, but serve also to deliver the line voltage of the generatorbetween the shortcircuited pairs. For this purpose, they must stand between the neutral zones. In these zones, on the other hand, there are other brushes 6 which deliver the charging current for the battery. The charging voltage will thus be greater than the line voltage in a proportion determined by the distance between the brushes and the distribution of the flux around the periphery of the armature.

Fig. 2 shows a suitable arrangement of the magnet core in a two-pole machine. Un-

drawing showsthe diagram' ot connections the'generaton Fig. 3

like the usual arrangement in such machines "fFigq'3 shows the aspect- 0ffafhalf-wave of battery. [Various devices have been pro posed for this p'urpose. According to the the fflux, counted from 'centerfto center of the auxiliary poles. "The 'ma'gnetomotive {force generated by the short-circuited armature conductors'varies substantially as' 'shown by the dotted CUIYB, while the flux', by reasonofthe variable reluctance, be repres'en't'edby the full cu'rve.

The voltage beiwv een"the brushes '6 will thuscorrespond tothe entire'liatche'd surface, and the volta'gebet'ween brushes 5 the middle rectangular surface. 'By suitably dimensioning the' pole 'arcs,lit is obviouslypossib'le' to obtainan desired "proportion betw'eenthes'e' rwsv ta-g'esand simultaneously the proportion between the armature-ampere turns generating the main flux and the resultantampere turns on the' 'auxiliary poles 8. By placing the brushes 5 in thegap be tweenth'e different 'polea'rcs, a good comage over a large range of speed and has for 'I'nutatiori' is obtained under these brushes. For improving the commutation under the brushes 6, which however carry less current, recesses may be made in the auxiliary poles corresponding to the commutation zones.

The counteracting winding 4 on the auxiliary poles 8 is preferably connected between the pairs of brushes 5, whereby the machine will endeavour to keep a constant voltage between these brushes. One series winding 9 traversed by the battery current and one 10 traversed by the load current proper (through the lamps 11) should be placed on the same poles for totally or partially compensating the armature reaction. For compensating the action of the resistance variations caused by temperature changes, resistances 12, 13 having low, or negative, temperature coefficient are prefer ably connected in parallel to the winding 1 and in series with the winding 4, respectively. As the resistance in the winding 1 increases by temperature rise, the current therein is reduced, since the resistance 3 acts to keep the current constant and the resistance 12 is comparatively constant. By suitably dimensioning the resistances 12 and 13 the said reduction of current in the winding 1 may be made proportional to the unavoidable reduction of current in the winding 4,

ran

Wheriby thg vjoltage o the lamp s' may kept approximately constant Incerta n cases it may be recommended to make this temperaturescompensationonly-partial v L Finally the chargingcurrenhthrough thel battery may be limited, in a manner known per so, by a resistaii'e 14, whereby said ourrenl is ILIUIQ LQgdily adapted to the state of charge of said battery.

laim s myli xenb on um. i i gi wmm jt' d a field h y a, i

gidsho t-cnci itedjbri shs and said other ii somer ne w h-IQ @rmfle; tur'e having 2i commntator' a-field ha v nghq y tem02 mai gp ls slend' e x ii 'y' P eb 1 zones ,0 f sai' mi having awmmukw n wm inh ie and aux lia y q ese tween, brus es short ciioiiiting portions of alctlng the T aforesaid al cominu taton'dfield core hav mmE-ms. 

